If this is all on the subject of a hypothetical follow up and not the current game...
Than I have to agree with the poster saying mobility should be enhanced. At the very least, Jump and roll should not be character specific abilities, they should be universal.
And while I understand the need to make sure the movement is balanced with skills so that defensive and specials that affect traversal aren't weakened or outight made useless, there is so much you could do with these skills moving forward that I don't believe it would end up an issue.
Take a skill like Dodge.
Ive used it in almost every arsenal I've ever made. It's the cornerstone of most of my strategies in this game. That said, it's one of the most basic moves in the game. Low cost, get it as soon as you start making arsenals, and it's common as dust.
Think about what could be altered just using that one skill and going from there:
A version of dodge that moves you underground like a crawl skill, completely avoiding projectiles and close range skills, but upon resurfacing leaves the user exposed.
A version that allows use in mid-air.
A version that increases the cost while extending the range.
A version that temporarily leaves a trail behind the user that causes damages to those who touch it at the cost of reduced range and increased cost. Think TRON-style.
A version that works closer to teleportation, allowing users to transport short distances and through objects based on current direction your heading (walking backwards would teleport you backwards). Imagine being able to phase right through the highway level's bottom street, right to the top.
I mean, that's 5 versions of the same skill, all of which would have distinct uses that enhanced mobility wouldn't negate. I could honestly make an entire category of skill purely based on mobility and nothing else.
Of course, this would all have to be balanced no differently than the current game has been, but the point I'm trying to make is that there's so much that could be done with what's there in terms of gameplay mechanics, it's hard to pin down what should be changed moving forward.